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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dec5b85f65ca60870b5ebb58108dacd43fe767eac4e4417a9b35497c2c3d51ec' 
  AND token = 'D9oCpVD2Mt8kQ2J69UgrCPehIi6MPGv68PiRJ1ElGZA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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