SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cac3ddf0013236b332ea932507d411f579303d94e4e81aeba31ec834fda904e' 
  AND token = '86gygbKiRcEKv9qtpVBbrN1qLMnomIk7pAayzLwEHoA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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