SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4955890f1074266232a04755534362b26c07997f4e8bf43575a4decf12d0784' 
  AND token = 'GId6Bda/yr3ICDSM9Xq8BO4J+nrQZbY9j7Qhnkbo1p8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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