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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75210001b6d2f191d05a515674c970d45ee3a3638cf9851641cad0bcb505f042' 
  AND token = 'MmNx9n3r9DVukmQrQWvd8SM7IWNt7S62ittShR8US8c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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