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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f68fcc36751a6f52a1c73a9e30e87b0f6e0942265841e03b681eed6434dcc30f' 
  AND token = 'FQI8VUN6OLxsTt7bg1LOyXi3BUSnoLSMh8SKeX9iJ0M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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