SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15e16770a790bfebc755eb5af25298279f43acd663f786a400eaf62f44d11adc' 
  AND token = 'BSE01unpG8eFFBrg+Jl9PMq61zEbeuxIBbEuv/7AS5g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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