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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18b544a13713f11a3da296b677793e83f996dda988574819a9f58673a12db382' 
  AND token = 'WfMngpC2ZIPAqv3QvuyseGz2nt6T/Td3iyKZQatvy4U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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