SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a551f13be569eee8261602ddef100172f9816847666bb86fb8a810aea0b7be76' 
  AND token = 'C/fWbAV1sFgIgzsd1kolUhH0M7dEjIwe8la2WaAO5G4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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