SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0751c99466cad4316db08036b94e477622f4c8fb7e5a15e43742f9c890f2ca6' 
  AND token = 'pjbmOukhnwwMycbKJVSPU5Bh6BJOPOmIod5QzF6+IR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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