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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4b9bec14ad97a40bb8d7eb9137cdf2404b885ae1d641f8492ad6e9e259befc78' 
  AND token = 'JWzmMdYztdQ5f18XHjWJnr2uEMlXYcgIvSo0sbrHRJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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