SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9bb0bf294b3af52924f06dc30f123a0b9591da1c4046258374143bb0f139ad0' 
  AND token = 'h6dcfTrKT9FaTatVRO0CY0i851n6zfH38i/RJLyGqbQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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