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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d51f5bb860a0d3652966d2009ce0563d865b51642b4c4e17a39126fc5d80346' 
  AND token = 'dnkhvR37ebB9i2Kn2eqRr6Oit3HlYY5Hf+ZLE9GIVik=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}