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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6b6c924958308608594ce2e3db6c86c28538f35714ebc7279d12d74cd0b1c9a' 
  AND token = 'iytlm+U+XDdqa7wy3RgQBPYE2rcH1GTo+VCXUyBd0dU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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