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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '502faea80141adb1dc34f91265f1fadfd4a7ecb1b256d64d08862d391d189fb6' 
  AND token = 'j3Rf7aSTlhGdNeHaFLjqiPpdyFGr3OGwrI3NkK+HBp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}