SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6518cf50669c879841f869ab263c3de5790bff604a0dc53bb83bff014bf1c00e' 
  AND token = 'FIygye2i+0PQaJeXCYBiv9g8lGJ1c+pTVsgA7/iBCMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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