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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3a8d8aa015439a842c6dee5d438cd8986886ad8407e45952a7e6ec81545a29c' 
  AND token = 'lA7CAGSMbxXD9UvrsV2QkWMtsP0rY4sZX3Z/wtk4I60=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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