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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dbae536891d0b919a12bedf902a7c4e71e9d2c22dac62f83c9a519652d1efb28' 
  AND token = 'zqOLQAvyG5bZrFopAErAbvuIMr9rTMFvcIz+XZWQNVM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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