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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1523b1f2052096b94473e3328b98fa47e88db688a411870ad6d4d89c9aeca08d' 
  AND token = 'rgIBUBnyiSQtUpq4tuyT0mrxqsaJdsh7YweCFcLso0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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