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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f08ef0e6c4ef8837cef4f9afa185043c28714b8558bffbe7a3ebbaf50ec0b309' 
  AND token = 'PFexx2H0wN8evNJt8sO76cQucC+EZQ6gTRRros+x9z8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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