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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c51f3552e3c984b8cc8f30a668542200ec8aa0399f2bc237a7d2634bbb095d10' 
  AND token = 'PSS1+iiF59L5c+RMSGc2DF9zoIxYu8UxUmIkY8reyh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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