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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8986504b7cc03ac1cb580a8d3e79eb45add3a18644df6d1564bd741b1546a75' 
  AND token = 'rQ6EbLaB4F3Gpm9De07AXbkyQwk7JVxTqd5iTdGJVbQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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