SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a90b787e9ccd8259f3394b20ac64fbaa8c51cea5e614bad5bd50fd3f519d7c51' 
  AND token = 'SUCQqrIFxqmpLMLerZdffmiXzoNfMn+EYDWRXrHNIeU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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