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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eaa939a4ae8b488c66747899bff26bb2fe5ba7806908cc1a41e1456087dea146' 
  AND token = 'Y7J66IKHhnQ8Xkgf5C/wQZ9DZh2kDgdEnC8DHfM4Qb0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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