SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '198fac12e8733123034bef33a5f88da4f5d509f22d429ae2204b3f258881c336' 
  AND token = 'a1l0gCmfc+UR9kLDNnZVrCP3T386qQZUugyHrWmaFdg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00062

JSON explain

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