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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'db2e635ab4758ee0cb267ccfb68fcc5999f4f86c22d371d42fa04d441c0c019f' 
  AND token = 'ne9knEQvk9LDGMA29CxX1YBo7wkd5v5AAenJHIvAUsk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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