SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '305ff2774188871cc1377a65b028f16961594cf02efbb34eaa582a208973223b' 
  AND token = 'KKntJuQSqJE8bDUKEMM54it8Wok35qPZEmxm2dvrQSY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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