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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1d1e381fe1dfaca0a496a406a261164d0115afce68c6a5a8e8c98ca307e335a8' 
  AND token = 'UHlwB371z2C9ztt0kDnQwZvqtfPATLvi5BXJ/XhH+4s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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