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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad2dd1cef2fe7eee9c643cb20c4279a518b2878ae1f0c096781e0502e0e2c0d7' 
  AND token = 'n8tp5Eb2B1xEiNwwWnqf+mRAMtQ5hjoNA8XnlfJQVnc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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