SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a960e7791f9bd504776da301c6da60b8eba40d7c26028ced1998b85449d3ad64' 
  AND token = 'cYTntMUJg7eBEgpqwuE3+3sGUsXc79gHvikqZXPVHwI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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