SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f4825f5ba9d9d23097070765356793361aaf22f90d6a21df652276b7051e01b' 
  AND token = 'OS2zlBsZAE030NDOdkEAUVN235CbBa95qFKNZw+TYv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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