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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be1a62a45883a64ea2cef72e7721d2136fb5559cb6b2595372a435526990c81a' 
  AND token = 'KFKqxbwK1XQz1xn77AwHMAux7iZhL8iHFMiRySg+bts=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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