SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cb6beede86298cc3755e65bbf0b07fb13df1b3526f27fd6f29f1eba3a3a2ebb' 
  AND token = 'fciaMKfjtNwYEOAiCaTAUv6tMmpyTsLRuRpGQN1YFUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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