SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42b8a9b11a0317f37ed3317f16f9183aa631412312b79795630a28e035999107' 
  AND token = '4kQZHe6wQ6u5pB825gjGC5zR6d+UVvKP/mTVCmMLlvQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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