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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '758463919ff9a184ae0e841218507509c3dc641187104d845ba628ccec079283' 
  AND token = 'k/3G8gK8sTaJTusjZSyz4gDaJRu59p+Psw6xuEga9Ic=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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