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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '763f031bb5215c83e7a597480b13f21a52742e51df69397dbb0511655a14785a' 
  AND token = '+RtunFA85KFZxT5XQd0enHuoECxdvYTqhAgj/GFF5dk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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