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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b78a37d2f4d3880ee1989b18f03f30c4817fae26d4016c7ce6b0b2ea2629c174' 
  AND token = 'poc7tb5TKc5+uxA5pxYXT8Ymk2ErzUGMto8VP0olwi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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