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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a3456413bffd8b7e164e1c38bba08021c881058e596edcc440dfdba196418db' 
  AND token = '5mji6ZfSUrSk2xAnZjoAZQF4RAlBkfCClEeuWfeVtPU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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