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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cb1543dfb6aba64c1529c4011d00e4282487f4b359b28e7e8551ee2009bcc443' 
  AND token = 'm8RKbPt1GtvXw0Z0SXUFJA/Elifabqq5XNFrnrdB5Hg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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