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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29b87fc509015d3f99fc3976990a24d0102803796c82c484e68b8e10b06bfd33' 
  AND token = '9zb8MCv3/sGvvun2lRZ2hAudYMe1CHnKzNflb037YvU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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