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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8f11d0ef944520df8700721de9a427893e38561e8ee3ecbdaf0cf836582b3a1' 
  AND token = '53zwiwcs25DmXTsUAHGptQRiojs5evX1aX1CJF3PSm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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